1. Field of the Invention
The present invention relates to a reciprocating motor, and more particularly, to a multi-windows type reciprocating motor having an outer core equipped with a pair of winding coils and a pair of magnets corresponding to the winding coils and arranged in two rows.
2. Background of the Related Art
FIG. 1 illustrates a side view of a reciprocating motor according to a related art and FIG. 2 illustrates a cross-sectional view of a reciprocating motor bisected along a line II—II in FIG. 1.
Referring to FIG. 1 and FIG. 2, a reciprocating motor according to a related art includes a fixed part S constructed with a multi type cylindrical outer core 10 and a cylindrical inner core 20 inserted into the outer core 10 leaving a predetermined gap, a pair of winding coils 30 and 30′ coupled inside the multi type outer core 10 or inner core 20, and a moving part 40 having magnets 41 and 41′ and inserted between the outer and inner cores 10 and 20 so as to reciprocate.
Besides, FIG. 1 and FIG. 2 illustrate exemplarily a structure that the winding coils 30 and 30′ are coupled with the multi type outer core 10.
Major components of the reciprocating motor according to a related art are explained in the following.
The multi type outer core 10 is constructed with a plurality of lamination sheets 11 stacked as a radial shape so as to form a cylindrical feature. Each of the lamination sheets 11 is a thin plate having a predetermined shape.
The lamination sheet 11, as shown in FIG. 2, is constructed with a horizontal path part 11a having a predetermined width and length so as to form an outer circumferential face of the multi type outer core 10 and first to third vertical path parts 11b, 11c, and 11d extending from a middle part and both ends of the horizontal path part 11a in a direction of a center of the core so as to have predetermined width and length.
The first to third vertical path parts 11b, 11c, and 11d are formed to leave predetermined intervals therebetween so as to form poles at the tips. Hence, a pair of coil-fitting grooves H and H′ are provided between the first to third vertical path parts 11b, 11c, and 11d. 
The coil-fitting grooves H and H′ are rectangular shapes of which one sides toward an inner circumferential face of the multi type outer core 10 are open.
The winding coils 30 and 30′ provided by winding coils as a ring type are inserted into the coil-landing grooves H and H′ of the multi type outer coil 10 so as to be mounted thereon.
Such a multi type outer core 10 is formed by leaving a predetermined interval between a pair of the winding coils 30 and 30′ in parallel with each other and by stacking the lamination sheets 11 along a pair of the winding coils 30 and 30′ cylindrically.
In this case, the lamination sheets 11 are stacked in a manner that the winding coils 30 and 30′ are inserted into the coil-fitting grooves H and H′.
Meanwhile, a plurality of lamination sheets 21 comprising a plurality of thin plates having a predetermined size are stacked radially one another so as to construct the cylindrical inner core 20. In this case, each of the lamination sheets 21 has a rectangular shape having a length corresponding to the length of the multi type outer core 10.
Such an inner core 20 is inserted into an inside diameter of the multi type outer core 10 coupled with the winding coils 30 and 30′ so as to have a predetermined gap from an inner circumferential face of the multi type outer core 10 in a radial direction.
The moving part 40, as shown in FIG. 1, includes a plurality of magnets 41 fixed to an outer circumferential face of a cylindrical magnet holder 42 in a circumferential direction. And, the magnets 41 and 41′, as shown in FIG. 2, are arranged on the outer circumferential face of the magnet holder 42 so as to form a pair of rows in a circumferential direction.
Namely, the magnets 41 and 41′ are constructed with two rows so as to confront a pair of the winding coils 30 and 30′ inserted in the coil-fitting grooves H and H′ of the multi type outer core 10.
A length L of each of the magnets 41 and 41′ is determined by adding a width w2 of the pole of the multi type outer core 10, i.e. a width of one of the vertical path parts of the lamination sheet 11 constructing the multi type outer core 10, to a width w1 of the coil-fitting groove H or H′.
Therefore, in the moving part 40, the magnets 41 and 41′ are arranged to confront the coil-fitting grooves H and H′ of the multi type outer core 10 so that the magnet holder 42 enables to carry out a reciprocating motion straightly between the multi type outer core 10 and the inner core 20 in accordance with a current flow.
Operation of the above-constructed reciprocating motor according to a related art is explained by referring to FIG. 3 and FIG. 4 as follows.
FIG. 3 and FIG. 4 illustrate cross-sectional views for explaining operational states of a reciprocating motor according to a related art.
Referring to FIG. 3, when currents are simultaneously applied in different directions respectively to a pair of the winding coils 30 and 30′ coupled with the multi type outer core 10, one flux is formed by the current flowing through the winding coil 30 in a clockwise direction (direction a) along the inner core 20 and multi type outer core 10 adjacent to the winding coil 30 located at a left side in the drawing.
Namely, generated is the closed-loop type flux having a path consisting of the first vertical path part 11b—horizontal path part 11a—second vertical path part 11c—inner core 20—first vertical path part 11b. 
At this moment, the other flux is formed by the current flowing through the winding coil 30′ in a counterclockwise direction (direction b) along the inner core 20 and multi type outer core 10 adjacent to the winding coil 30′ located at a right side in the drawing.
Namely, generated is the other closed-loop type flux having a path consisting of the third vertical path part 11d—horizontal path part 11a—second vertical path part 11c—inner core 20 —third vertical path part 11d. 
Therefore, the moving part 40 including the magnets 41 and 41′ moves toward the right direction (direction A) of the drawing by a reciprocal reaction of a pair of the fluxes formed by the currents flowing through the winding coils 30 and 30′ and the other pair of the fluxes formed between the multi type outer core 10 and inner core 20.
On the contrary, if the directions of the currents applied to a pair of the winding coils 30 and 30′ are switched, as shown in FIG. 4, one flux is formed by the current flowing through the left winding coil 30 in a counterclockwise direction (direction b) along the inner core 20 and multi type outer core 10 adjacent to the left winding coil 30 as soon as the other flux is formed by the current flowing through the right winding coil 30′ in a clockwise direction (direction a) along the inner core 20 and multi type outer core 10 adjacent to the right winding coil 30′.
Therefore, the moving part 40 including the magnets 41 and 41′ moves toward the left direction (direction B) of the drawing by a reciprocal reaction of a pair of the fluxes formed by the currents flowing through the winding coils 30 and 30′ and the other pair of the fluxes formed between the multi type outer core 10 and inner core 20.
Thus, the above-explained reciprocating motor enables the moving part 40 having the magnets 41 and 41′ to carry out a reciprocating motion by alternating directions of the currents flowing through a pair of the winding coils 30 and 30′ in different directions.
However, the above-explained reciprocating motor according to a related art results in the following problems.
FIG. 5 illustrates a diagram for a state of a magnetic flux generated by a pair of magnets 41 and 41′ in a reciprocating motor according to a related art, in which the moving part 40 has moved most to the left side.
Referring to FIG. 5, fluxes are formed at the third vertical path part 11d in directions opposite to each other by a pair of the magnets 41 and 41′, thereby failing to cancel the fluxes each other. Yet, magnetic saturation may occur at the first and second path parts 11b and 11c due to relatively large flows of the fluxes.
Namely, as each of the lamination sheets 11 constructing the multi type outer core 10 has a single sheet structure, the flux generated by the first magnet 41 flows to the third vertical path part 11d and the other flux by the second magnet 41′ flows to the first vertical path part 11b. Hence, other path parts failing to be adjacent to the first and second magnets 41 and 41′ are affected by such fluxes.
Thus, during the process of forming the fluxes in the lamination sheets, as shown in FIG. 5, the flux (of the third vertical path part) is cancelled but the other fluxes (of the first and second vertical path parts) are merged to generate the magnetic saturation.
Therefore, the above-explained reciprocating motor according to the related art has to design the parts of the respective path parts in the lamination sheets 11 constructing the multi type outer core 10 so as not to generate the magnetic saturation, thereby having difficulty in designing a motor.
FIG. 6 illustrates a diagram for the flux states generated by the current flows of a pair of the winding coils 30 and 30′ in a reciprocating motor according to a related art, in which the fluxes generated from the winding coils are affected reciprocally due to the single-sheet-structured lamination sheets 11 constructing the multi type outer core 10 when the currents flows through a pair of the winding coils 30 and 30′ respectively in directions opposite to each other.
Referring to FIG. 6, the fluxes generated by the respective winding coils 30 and 30′ flow through the first and third vertical path parts 11b and 11d in opposite directions, thereby reducing the fluxes. As the polarities working reciprocally with the magnets 41 and 41′ decrease, so does a motor constant which is an important factor affecting an efficiency of a motor.
Moreover, as shown in FIG. 2, sizes of the magnets 41 and 41′, which are determined by the opening widths w1 of the coil-fitting grooves H and H′ and the widths w2 of the poles, are so large that supply of the magnets demands sufficient amount. Thus, a manufacturing cost rises.